Thanks to Iain for letting me know that choir seats for the trio concert at the Royal Festival Hall in London on July 25, 2009 are still available from Southbank Centre (for 45 British Pounds).
According to De Standaard and Nieuwsblad, Keith Jarrett will play a solo concert at the Palais des Beaux-Arts in Brussels on October 9, 2009. Tickets will cost from 40 EUR to 100 EUR and will be available from Bozar Music. Update: tickets can already be ordered by phone (thanks Matthias!).